This project will generate extensive new findings about the organization, connectivity, and evolutionary relationships of cerebral cortex in humans and nonhuman primates. It will also disseminate the results by establishing a user-friendly database that provides ready access to high-resolution atlases, reference data, and extensively processed published datasets. This will enable investigators to compare their results with the reference data and provide a platform to share their own results. Taken together, these efforts will accelerate progress in understanding human brain circuits in health and disease. The first aim is to obtain more accurate maps of anatomical connectivity in the macaque monkey and to compare anatomical connectivity with tractography methods that indirectly estimate connectivity based on diffusion imaging MRI scans. An existing dataset, involving dozens of retrograde tracer injections charted on digitized histological sections, will be mapped onto a high-resolution macaque atlas. This will yield quantitative maps of 'ground truth' neuroanatomical connectivity with unprecedented accuracy. Comparing tracer-based maps with results from tractography applied to postmortem macaque brains, will provide an objective analysis of how well tractography estimates anatomical connection strengths. The second aim will compare cortical organization and connectivity in humans to that in the macaque monkey and also our closest living relative, the chimpanzee. Surface-based registration between species will be used to evaluate candidate evolutionary homologies between cortical areas and to compare connectivity patterns between macaque and human. Chimpanzee cortex will be compared to human and macaque cortex using myelin maps as a common marker of cortical architecture. These analyses will better characterize regions of rapid evolutionary expansion in the human lineage. The third aim will establish and help populate a new database, the Brain Analysis Library of Spatial maps and Atlases (BALSA). BALSA will include a curated, up-to-date repository of reference data accurately mapped to atlas surfaces and volumes, plus a library for sharing extensively analyzed datasets associated with published studies, as voluntarily submitted by authors. BALSA will have user-friendly features that enable easy data uploading and facilitate browsing, searching, web-based visualization, and downloading datasets of interest.